(1) Field of the Invention
This invention relates to a radiation grid for removing scattered radiation, a radiographic apparatus equipped therewith, and a method of manufacturing the radiation grid. More particularly, the invention relates to a radiation grid which does not need spacers for gaps between adjacent absorbing foil strips, a radiographic apparatus equipped therewith, and a method of manufacturing the radiation grid.
(2) Description of the Related Art
Radiographic apparatus for acquiring fluoroscopic images of patients include a type that emits cone-shaped radiation beams from a radiation source toward a patient, and detects radiation transmitted through the patient with a flat panel detector (hereinafter abbreviated as FPD). Such fluoroscopic images are subject to scattered radiation incident on the FPD after being scattered within the patient during passage through the patient. This becomes a factor for worsening the contrast of the fluoroscopic images. A radiation grid may be provided to cover a radiation detecting plane of the FPD for blocking the scattered radiation incident on the FPD (see Japanese Unexamined Patent Publication No. 2008-168110).
The construction of a conventional radiation grid will be described. As shown in FIG. 1, a conventional radiation grid 71 includes absorbing foil strips 72 formed of lead which easily absorbs radiation, and spacers 73 which support the foil strips 72 to maintain the latter in a linear shape. The absorbing foil strips 72 and spacers 73 are arranged alternately to form a plate-like absorber. Further, grid covers are provided to sandwich the plate-like absorber in between. With the radiation grid 71, direct radiation which proceeds to penetrate the patient mostly passes through the gaps (i.e. spacers 73 to be precise) between adjacent absorbing foil strips 72. Conversely, most of the scattered radiation is incident on the absorbing foil strips 72 to be absorbed there.
In order to obtain a fluoroscopic image with increased sharpness, it is desirable to have a construction which does not include the spacers 73 obstructive to advance of the direct radiation. So, in recent years, a radiation grid without the spacers 73 has been developed. The construction of such a radiation grid will be described. A radiation grid 71 has a pair of grid covers covering an absorber 84. Since the radiation grid 81 has no spacers, each of the absorbing foil strips 82 is fixed by being bonded to the grid covers.
However, the conventional construction has the following problem.
When manufacturing the conventional radiation grid 81, the absorbing foil strips 82 will deform. According to a conventional method of manufacturing the radiation grid 81, it is necessary, after bonding the absorbing foil strips 82 and grid covers 85 and 86, to shape the absorbing foil strips 82 by cutting ends thereof protruding from the grid covers 85 and 86. Each of the absorbing foil strips 82 is supported only by the grid covers 85 and 86, with nothing provided between the absorbing foil strips 82. Therefore, under the stress of a cutting operation, the absorbing foil strips 82 will readily deform. Since the absorbing foil strips 82 become distorted at cut sections, the conventional manufacturing method cannot manufacture the radiation grid 81 with the absorbing foil strips 82 arranged in an orderly manner.